Patent Application
20160227681
It is well known that the operation of some electronic circuits found within industrial and consumer electronics devices can produce radio frequency (RF) electro-magnetic waves capable of interfering with other electronic circuits. This problem is often referred to as electro-magnetic interference (EMI). To mitigate EMI, it is common to install an EMI shield within a device around those components known to generate such unwanted electro-magnetic energy to prevent further propagation of the energy. The EMI shield, typically made from an Aluminum or similar conducting metal usually coupled to a device ground, acts as a high resistance barrier that significantly attenuates the power level of the RF electro-magnetic waves. EMI shields are typically soldered or otherwise semi-permanently mounted into position so that they cannot be easily removed by the end consumer and may be designed so that any tampering with the shied is readily evident.
A difficulty arises however with respect to a unit that needs repair or testing where the EMI shield blocks necessary access to one or more components or test points. Removal of the EMI shield may require de-soldering that is time intensive and therefore expensive. Further, heat from the de-soldering process can damage components proximate to the shield. Two piece EMI shields are one solution that has been proposed to address the need to access components hidden behind EMI shielding. For example, the EMI shield may include a door or window that can be mechanically opened and closed. However, two piece EMI shields are considerably more complex than one-piece shield to fabricate and correspondingly more expensive.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for systems and methods for serviceable EMI shielding.
The Embodiments of the present invention provide methods and systems for providing serviceable EMI shielding and will be understood by reading and studying the following specification.
Systems and methods for serviceable EMI shielding are provided. In one embodiment, an electronics device comprises: a circuit board; at least one component mounted to the circuit board; an electro-magnetic interference (EMI) shield that encloses the at least one component within a volume of space, wherein the EMI shield comprises: a sheet of shielding material shaped to define a shield fence and a shield cover, wherein the shield fence is mechanically attached to a surface of the circuit board and extends away from the surface; and a kiss-cut feature in the sheet of shielding material between the shield fence and the shield cover.
Embodiments of the present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present invention. Reference characters denote like elements throughout figures and text.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.
Embodiments of the present disclosure provide system and methods for EMI shielding that facilitates cost efficient rework and testing of devices without putting undue stress on other board components which can shorten the product life or further damage the product. Devices may be produced using a one piece shield that comprises an inexpensive kiss-cut feature. If a device never needs service, then the one piece shield remains in-place and intact for the life of the product. For those devices that do require service, the kiss-cut feature allows a portion of the original shielding material to he peeled off to gain access to components within the shielded area. The balance of the original shielding material (referred to herein as a shield fence) remains attached to the device and forms a base upon which a replacement shield cover can be easily affixed. In one embodiment, the replacement shield cover is implemented using a snap-on post-repair cover that is installed over the shield fence. In another embodiment, the replacement shield cover is implemented using a shielding film cover that is applied to the shield fence using a conductive adhesive.
The shield fence 124 is mechanically attached to PCB 110, and extends away from the surface 113 of PCB 110. The shield fence 124 is positioned around a periphery of an area 114 on the surface 113 of PCB 110 that includes the components 115 to be shielded. In one embodiment, shield fence 124 is rigidly attached to PCB 110. For example, shield fence 124 may be soldered to PCB 110 or otherwise rigidly attached to surface 113 using an adhesive. Although in some embodiments shield fence 124 may comprises a continuous ring of material around the shielded area 114, in others it is not. For example, shield fence 124 may be discontinuous and include one or more voids 127 around the periphery of the shielded area 114 (for example where a penetration is needed to feed through a wire or cable). Shield cover 125, which as mentioned above is mechanically part of the same sheet of shielding material 122 as shield fence 124, extends over the area 114 that includes the components 115, enclosing the components within a volume defined by PCB 110, shield fence 124 and shield cover 125. As shown in
It should be noted that shield fence 124 may remain mechanically attached to PCB 110. That is, in most cases there is no need to remove shield fence 124 to obtain access to components 115 to perform testing, repair, or other rework. But it should be noted that if for some reason removal of shield fence 124 from PCB 110 is desired, this can be more easily accomplished with shield cover 125 detached. For example, EMI shields are very often secured to their host PCB using solder that must be heated to reflow to enable the shield's removal. Removal of shield cover 125 permits application of heat (using soldering iron, for example) with more precision directly to target portions of shield fence 124 within area 114 as well as outside area 114. Further, because shield cover 125 is removed, thermally energy is not lost heating the mass of shield cover 125 while attempting to obtain reflow of the solder holding shield fence 124 to PCB 110. More of the applied heat is efficiently conducted through the shield fence 124 to the solder, requiring less total heat to be applied for a shorter time and avoiding damage to surrounding components from unnecessary exposure to heat.
In some embodiments, shield cover 125 may further comprise a lift feature such as a pry hole 180 or lift tab 182 such as shown in
Once rework and testing is finished, to return the device to service, a replacement shield cover to restore EMI shielding is required. In one embodiment, a snap-on post-repair cover 310 is installed onto shield fence 124, such as shown in
In some applications, EMI shielding tamper prevention, or at least tamper detection, may be an important consideration.
As shown in
The resulting seal from adhering shielding film cover 410 to shield fence 124 need not be airtight, but merely exhibit high resistance to RF waves. Attempts to remove the cover 410 will result in the material tearing, revealing and thus discouraging tampering. Further, if subsequent repairs are needed, the shielding film cover 410 may be torn away, the repair performed, and a new shielding film cover 410 applied.
In one embodiment, the film material 430 of shielding film cover 410 may comprise, for example, a substrate of polycarbonic material or a PET (Polyethylene Terephthalate) film coated with the one or more metallization layers 432 which may comprise tin, aluminum, copper, or other metallic alloy. The thickness of the metallization layer may be tailored to obtain the desired electrical resistance for the RF wave that is to be blocked. For example, in one embodiment, the metallization layer 432 is a tin layer on the order of 0.001-0.005 inches thick.
In one embodiment, shielding film cover 410 may be provided in the form of a pre-cut part sized and shaped at manufacture to accommodate the size and shape of the shield fence to which it will be applied. In other embodiments, shielding film cover 410 may be provided as a sheet of material that may be trimmed to the needed shape and size when applied. In one such embodiment, the shielding film cover 410 may include pre-patterned guides or kiss-cuts to facilitate trimming.
Example 1 includes an electronics device, the device comprising: a circuit board; at least one component mounted to the circuit board; an electro-magnetic interference (EMI) shield that encloses the at least one component within a volume of space, wherein the EMI shield comprises: a sheet of shielding material shaped to define a shield fence and a shield cover, wherein the shield fence is mechanically attached to a surface of the circuit board and extends away from the surface; and a kiss-cut feature in the sheet of shielding material between the shield fence and the shield cover.
Example 2 includes the device of claim 1, wherein the shield fence is positioned around a periphery of an area on the surface of the circuit board that includes the at least one component.
Example 3 includes the device of claim 2, wherein the shield fence is discontinuous.
Example 4 includes the device of any of claims 1-3, wherein the shielding material comprises a conducting material.
Example 5 includes the device of claim 4, wherein the conducting material comprises aluminum or copper.
Example 6 includes the device of any of claims 1-5, wherein the kiss-cut feature comprises a partial cut through the top surface of the sheet of shielding material along a path that facilitates detachment of the shield cover from the shield fence.
Example 7 includes the device of any of claims 1-6, wherein the shield fence comprises one or more dimples protruding out from the shield fence.
Example 8 includes an electronics device, the device comprising: a circuit board; at least one component mounted to the circuit board; an electro-magnetic interference (EMI) shield that encloses the at least one component within a volume of space, wherein the EMI shield comprises: a shield fence positioned around a periphery of an area on a surface of the circuit board that includes the at least one component, wherein the shield fence is mechanically attached to a surface of the circuit board and extends away from the surface; and a shielding film cover attached to the shield fence by an electrically conducting adhesive.
Example 9 includes the device of claim 8, wherein the shield fence is discontinuous.
Example 10 includes the device of any of claims 8-9, wherein the shield fence comprises a conducting material.
Example 11 includes the device of claim 10, wherein the conducting material comprises aluminum or copper.
Example 12 includes the device of any of claims 8-11, wherein the shielding film cover comprises: a film material coated with one or more metallization layers; and a layer of the electrically conducting adhesive applied to the one or more metallization layers.
Example 13 includes the device of claim 12, wherein the film material comprises a Polyethylene Terephthalate (PET) film.
Example 14 includes the device of any of claims 12-13, wherein the one or more metallization layers comprise tin, aluminum, copper, or a metallic alloy.
Example 15 includes a method for accessing shielded components on an electronics device, the method comprising: applying a mechanical force to a shield cover of an electro-magnetic interference (EMI) shield, wherein the EMI shield comprises a shield fence mechanically attached to a circuit board and the shield cover is mechanically attached to the shield fence by a kiss-cut feature; tearing the shield cover from the shield fence along the kiss-cut feature; and removing the shield cover from the shield fence.
Example 16 includes the method of claim 15, further comprising: restoring EMI shielding by snapping a replacement shield cover over the shield fence.
Example 17 includes the method of any of claims 15-16, further comprising: restoring EMI shielding by applying a shielding film cover over the shield fence.
Example 18 includes the method of claim 17, wherein the shielding film cover comprises: a film material coated with one or more metallization layers; and a layer of electrically conducting adhesive applied to the one or more metallization layers.
Example 19 includes the method of claim 18, wherein the film material comprises a Polyethylene Terephthalate (PET) film.
Example 20 includes the method of any of claims 18-19, wherein the one or more metallization layers comprise tin, aluminum, copper, or a metallic alloy.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
